If-Then-Else Is a Code Smell

In most cases (maybe even in all of them), if-then-else can and must
be replaced by a decorator or simply another object.
I've been planning to write about this for almost a year but only today found
a real case in my own code that perfectly
illustrates the problem. So it's time to demonstrate it and explain.

Take a look at the class
DyTalk
from
yegor256/rultor
and its method
modify().
In a nutshell, it prevents you from saving any data to the DynamoDB if there were no
modifications of the XML document. It's a valid case, and it has to be
validated, but the way it's implemented is simply wrong. This is
how it works (an oversimplified example):

What's wrong, you wonder? This if-then-else forking functionality doesn't really belong
to this object—that's what's wrong. Modifying the XML document
and saving it to the database is its functionality, while
not saving anything if the modification instructions set is empty is not
(it's very similar to defensive programming).
Instead, there should be a decorator, which would look like this:

Now, if and when we need our talk to be more clever in situations where
the list of directives is empty, we decorate it with QuickTalk.
The benefits are obvious: the DyTalk class is smaller and therefore
more cohesive.

But the question is bigger than just that. Can we make a rule out of it? Can we say that
each and every forking is bad and should be moved out of a class? What about
forking that happens inside a method and can't be converted to a decorator?

I'm suggesting this simple rule: If it's possible to convert if-then-else forking
to a decorator, it has to be done. If it's not done, it's a code smell.
Make sense?